Piston for fluid pressure cylinders



Dec. 30, 1952 p, AUDEMAR 2,623,501

PISTON FOR FLUID PRESSURE CYLINDERS Filed March 1, 1948 2 Sl-IEETS-SHEET 1 //V VZ/V 70/? Puma Al/00MB Dec. 30, 19 52 P. AUDEMAR PISTON FOR FLUID PRESSURE CYLINDERS Filed March 1, 1948 Q .8 m m M H /m x. x 1 MIA H I I. W *x N\ m \m Patented Dec. 30, 1952 atzaso'i asses FOR FLUID rnnssmm "CYLINDERS Pierre Audeinar, Villesn '61 France :Societ Olaer Marine,

es, France, assignoi: to Paris, France, a company Application March 1, 1948, Serial No. 12,305 In France September .28, 194.6

Section 1, Public Law 690, a gilstaieis Patent expires September 28, 1966 6 Claims.

The present invention relates to "pistons for liydifaii s or Dnum'a'ticfiuid pressure cylinders in which there is high fluid pressure acting on the working time or faces of the iiiston.

It is known that in fluid pressure cylinders in which the pressures or the Working fluid such as a gas or liquid acting on the working face or races o'f-"a not well centered piston are very high, the pressure fluid which may leak between a circurnferential portion of the piston and a corresponding portion of the inner cylinder wall into the space behind the piston when the same is at Jrest will press the piston against a portion of the inner wall of the cylinder so as to destroy, in the case of a pressure fluid such as oil, the oil 'filmf b'etween piston and cylinder, thus creating a resistance or additional friction whichconstitutes-a -siib'stantial loss of energy and requires a substantial increase of power to displace the piston along the cylinder wall.

It is the object, therefore, of the present invention to provide an improved piston structure for fluid pressure cylinders which greatly reduces the risk of the piston being pressed against the cylinder wall by the pressure fluid leaking between a circumferential portion of the piston and cylinder into the space behind the piston when the same is at rest.

The accompanying drawings show as examples three embodiments of the invention.

Fig. 1 shows an axial section of a jack or similar servo-motor built in the usual way;

Figiz is a similar axial section of a jack constructed according to the invention;

.Fg. 3v is a transversal section showing more or lessdiagrammatically the phenomenon that takes place in the ordinary jack shown in Fig. 1, when thejlpiston is submitted to a very high pressure;

1 18.54 is a transversal section through the piston .ofiFig. 2;

Fig.5 is an axial section of a second embodiment of the invention applied to a selector valve;

Fig. '6 is a transversal section of the piston and cylinder shown in Fig. 5;

Fig. ,7 shows the application of the invention to fa slide valve.

1 still indicates the piston and z the cylinder. According to the invention, the part or segment 3 o'f-the piston on the high pressure side is ofrelatiyely reduced diameter with respect to the remaining part or segment of the pistonloca ted on the low pressure side. A peripher i'c groove '5 is provided between the two parts or segments, while passages 4, provided i'nthe periphery of the remaining part along dir'ectrixes thereof establish a communication between the groove 3 and the low pressure side of th jack provided with the exhaust '6. As shown in Fig. 4, withsuch an ar rangement, the piston is well centered and the risk of stickin is completely eliminated. One

must note that, for the clarity of "the drawings,

the difference between the diametei-v th segments of the piston has been voluntary ease- 3 geratd.

directly on the ball 9.

In the embodiment of Fig. 7, the invention is 0 shown applied to a selector valve or distributor having a double piston.

The fluid under high pressure arrives at P. The orifices l8 and I9 are set either for the admission or for the exhaust through I6. An axial passage l i is established which providesa communication between the two outer faces it of the double piston. The two grooves 5 communicate with this axial passage 14 through radial holes l3,

. while radial holes I5 establish a communication Referring first to Figs. 1 and 3, one sees a piston c I working in a cylinder 2. Under the effect of th;.high pressure arriving in P, the piston tends to stick against the wall of the cylinder 2 and takes finally the eccentric position shown in Fig. 3, in which the lubricant film is destroyed in the zone 1.

I'n th'e first embodiment of the invention, shown applied to a jack or servo-motor in Figs. 2 and 4,

between the left hand side end sage l4 and the left hand low What I claim is: p 1. The combination with a cylinder-piston device having a high fluid pressure side and a low pressure side: of means to prevent the piston from of said axial paspressure side l1.

being pressed against a portion of theinner wall of the cylinder under the action of the; radial components of the fluid pressure applied on the high pressure side of the device; said means comprising in the piston a segmental portion of relatively reduced transversal section and relative fluidtightness on the high pressure side, a segmental portion of normal transversal section on. the low pressure side, a peripheric groove between said two portions and a passage or passages establishing a communication between said groove and the low pressure side of the device.

2. In a cylinder-piston device having a high fluid pressure side and a low pressure side a piston comprising: a segment of relatively reduced transversal section on the high pressure side to establish a relative tight connection with the M =larger diameter bein tightly-fitted in said cylin- "der'and the parts of smaller diameter having a relative fluid-tightness, said parts of the smaller diameter facing each other in said median-high fluid pressure space; and-anaxial passage, pro- 'vided through the double piston, establishing a communication between said two low pressure spaces; and radial orifices establishing a communication between said axial passage and said two grooves.

4. A piston for hydraulic or pneumatic fluid pressure cylinders, comprising an extension on the working face of the piston, said extension leeing of slightly reduced diameter with respect to that of said piston so as to have a loose fit in h Cylinder, and means to establish communication-between the space around said extension and the space at that side of said piston remote from said extension, whereby any fluid leaking around said extension is prevented from leaking between the piston and the inner wall of the cylinder when the piston is at rest.

5. A piston for hydraulic or pneumatic fluid pressure cylinders, comprising an extension on the working face of said piston, said extension being of slightly reduced diameter with respect to that of said piston so as to have a loose fit in the cylinder, an annular groove provided on said extension adjacent said working face, and at least one longitudinal groove formed in the wall of said piston to establish communication between said annular groove and the space at that side of said piston remote from said extension, whereby any fluid leakingaround said extension into said annular groove is prevented from leaking between the piston and the inner wall of the cylinder when the piston is at rest.

6. A piston for hydraulic or pneumatic fluid pressure cylinders, comprising an extension on the working face of the piston, said extension being of slightly reduced diameter with respect to that of said piston so as to have a loose fit in the cylinder, an annular groove provided on said extension adjacent said,work-ingface, anaxial bore provided in the face of said piston opposite its working face, and at least one radial passage leading from said annular groove 'to said axial bore, whereby any fluid leaking around said extension into said annular groove will escape through said radial passage and said axial bore when the piston is at rest.

PIERRE AU-DEMAR.

REFERENCES CITED The following references are of record in th file of this patent: I

UNITED STATES PATENTS Levy July 28, 1942 

